From the Guidelines
Diagnosing Hepatitis C Virus (HCV) infection involves a step-by-step approach. The first step is to test for HCV antibody using either a rapid or laboratory-conducted assay, which can indicate current or past HCV infection, or false positivity 1.
Steps for Diagnosing HCV Infection
- Initial Testing for HCV Antibody: An FDA-approved test for HCV antibody should be used, with outcomes reported as reactive or nonreactive 1.
- Testing for HCV RNA: If the HCV antibody test is reactive, an FDA-approved NAT assay should be used to detect HCV RNA in serum or plasma, indicating current HCV infection 1.
- Reflex Testing: Reflex testing, where HCV RNA is tested in the same sample as the HCV antibody test, can increase the proportion of patients who receive subsequent linkage to care 1.
- Point-of-Care Tests: Point-of-care tests, such as antibody detection in saliva or RNA detection via fingerstick blood sampling, can provide quick and accessible results, especially in settings with limited resources 1.
- Dried Blood Spot Testing: Dried blood spot testing can facilitate sample collection and simultaneous screening for co-infections, such as HIV 1.
Special Considerations
- Immunocompromised Patients: For patients who are immunocompromised, testing for HCV RNA can be considered, as anti-HCV may not be detectable in these patients 1.
- Recent Exposure: For persons who might have been exposed to HCV within the past 6 months, testing for HCV RNA or follow-up testing for HCV antibody is recommended 1.
- False-Positive Results: False-positive results for anti-HCV can occur, and HCV RNA testing is necessary to confirm the diagnosis 1.
From the Research
Steps for Diagnosing Hepatitis C Virus (HCV) Infection
The diagnosis of HCV infection involves several steps, including:
- Initial screening using serological assays to detect anti-HCV antibodies in the patient's serum or plasma 2, 3
- Confirmatory testing using molecular assays, such as qualitative and quantitative HCV RNA tests, to detect the presence of the virus and determine viral load 2, 3
- Genotyping to identify the dominant strain of the virus, which is essential for guiding treatment 2, 3
- Additional biomarker assays to assess liver function and enable disease staging 3
Laboratory Diagnostic Tests
Specific laboratory diagnostic tests for HCV infection can be categorized into two main types:
- Serological antibody tests, which detect anti-HCV in serum or plasma 2, 4
- Molecular tests, which detect HCV RNA genome, investigate viral load, and determine the characteristics of the genome 2, 3, 4
Strategies for Diagnosis
Strategies for diagnosis and monitoring of HCV infection vary depending on the setting and goal:
- In low-risk settings, such as blood banks, a positive anti-HCV result should be confirmed with an analytical antibody test, followed by a HCV RNA test 2
- In high-risk populations or situations where HCV infection is suspected, a positive anti-HCV result is likely to be true positive, and confirmation with a HCV RNA test is significant 2
- Quantitative HCV RNA testing and genotyping should be performed if therapy is considered 2
Recent Advancements
Recent studies have developed novel diagnostic assays, such as the HCV antigens enzyme immunoassay (HCV-Ags EIA), which can detect HCV infection in one step with high sensitivity and specificity 5 Additionally, advancements in hepatitis C diagnostics and the US regulatory landscape have created opportunities to improve hepatitis C diagnosis and include viral-first testing strategies 6